Green Airlines

Rankings / Routes / Chicago to Washington, DC

2025 flights

Chicago to Washington, DC

Between Chicago and Washington, DC, 3.3 million passengers flew nonstop in 2025, on 30 thousand flights of about 609 miles and 1.5 hours in the air. The average passenger accounted for about 121 kg of CO2 from the fuel burned, from 86 kg on Frontier Airlines to 181 kg on Republic Airways.

  • 121 kgCO2 per passenger, average
  • 609 milesabout 1.5 hours in the air
  • 3.3 millionpassengers in 2025
  • 74%of seats filled

CO2 per passenger, airline by airline

CO2 per passenger by airline, Chicago to Washington, DCBar chart of kilograms of CO2 per passenger on each airline between Chicago and Washington, DC in 2025.050100150Frontier Airlines86 kgSouthwest Airlines109 kgUnited Airlines119 kgAmerican Airlines132 kgEnvoy Air174 kgRepublic Airways181 kg
CO2 per passenger by airline, Chicago to Washington, DCBar chart of kilograms of CO2 per passenger on each airline between Chicago and Washington, DC in 2025.050100150Frontier Airlines86 kgSouthwest Airlines109 kgUnited Airlines119 kgAmerican Airlines132 kgEnvoy Air174 kgRepublic Airways181 kg
Kilograms of CO2 per passenger, one way, 2025. Fuel burned only. Less is better.
Chicago to Washington, DC by airline, 2025
AirlineShare of passengersFlights (thousands)Main aircraftSeats per flightSeats filledkg CO2 per passenger
United Airlines46%13.0Airbus A320-200, Airbus A31915675%119
Southwest Airlines29%8.3Boeing 737-700, Boeing 737 MAX 816170%109
American Airlines17%5.1Airbus A319, Boeing 737-80015073%132
Envoy Air3%1.8Embraer 1756987%174
Republic Airways2%1.3Embraer 1757675%181
Frontier Airlines2%0.5Airbus A320neo, Airbus A32119275%86

What explains the differences

It's number 21 of the 100 busiest city pairs by passengers, and number 84 for the lowest CO2 per mile flown (0.20 kg per passenger-mile, number 1 being the lowest). A typical route of 609 miles in this set comes out at about 103 kg, so this one is 17% above it.

The flights use more than one pair of airports: DCA to ORD (39%), IAD to ORD (17%), BWI to ORD (16%). The figures here cover all of them.

The airlines on this route differ by 111% per passenger. Frontier Airlines burned 1,264 gallons per flight and 144 passengers on each, and Republic Airways 1,050 gallons and 57 passengers. The gap comes from how many passengers share each flight, not from fuel burned per flight. Frontier Airlines flew 75% full here against 75% for Republic Airways, flying mostly Airbus A320neo against Embraer 175.

For comparison, the EPA default factor for a flight of this length (0.129 kg per passenger-mile) would give 79 kg. The EPA figure is a national average for flights of that length. The measured figure for this route is 54% higher.

2019 compared with 2025

In 2019 the route carried 3.7 million passengers on 34 thousand flights. In 2025 it carried 3.3 million, down 12%, on 30 thousand flights, down 10%. The average flight had 139 seats then and 148 now, and 79% of them were filled against 74%.

CO2 per passenger was 117 kg in 2019 and 121 kg in 2025, up 3.6%. Fuel burned per flight was up 2.2% (1,322 gallons to 1,352) and passengers per flight were down 1.3% (110 to 109). The distance flown was about the same (609 miles then, 609 now).

United Airlines led in both years, with 36% of passengers in 2019 and 46% in 2025. American Airlines lost the most, 24% to 17%. Frontier Airlines didn't have 1% of the passengers in 2019 and now carries 2%. Spirit Airlines and SkyWest Airlines no longer reach 1% of passengers, having had 7% in 2019.

Airline by airline, Southwest Airlines went from 109 kg to 109 kg per passenger (147 seats per flight to 161, main aircraft Boeing 737-700 in both years); American Airlines went from 117 kg to 132 kg per passenger (161 seats per flight to 150, main aircraft Boeing 737-800 then and Airbus A319 now).

Chicago to Washington, DC, 2019 and 2025
Measure20192025
Passengers (thousands)3,7333,301
Flights (thousands)33.930.3
Seats filled79%74%
Gallons of fuel per flight1,3221,352
kg CO2 per passenger117121
CO2 per passenger by airline, 2019 and 2025, Chicago to Washington, DCBar chart of kilograms of CO2 per passenger on Chicago to Washington, DC for each major airline in 2019 and in 2025.050100150United Airlines 2019114 kgUnited Airlines 2025119 kgSouthwest Airlines 2019109 kgSouthwest Airlines 2025109 kgAmerican Airlines 2019117 kgAmerican Airlines 2025132 kgEnvoy Air 2019184 kgEnvoy Air 2025174 kg
CO2 per passenger by airline, 2019 and 2025, Chicago to Washington, DCBar chart of kilograms of CO2 per passenger on Chicago to Washington, DC for each major airline in 2019 and in 2025.050100150United Airlines 2019114 kgUnited Airlines 2025119 kgSouthwest Airlines 2019109 kgSouthwest Airlines 2025109 kgAmerican Airlines 2019117 kgAmerican Airlines 2025132 kgEnvoy Air 2019184 kgEnvoy Air 2025174 kg
Kilograms of CO2 per passenger on the airlines that flew the route in both years. 2019 figures use that year's filings and estimated aircraft fuel rates, with type-average replacements for missing or outlying filings as described in the methodology. Less is better.

Chicago to Washington, DC and back: time in the air

Flights from Washington, DC to Chicago spent 98 minutes in the air on average in 2025, against 84 minutes from Chicago to Washington, DC: 14 minutes longer, 16% more. That's the westbound direction, into the prevailing west-to-east winds, which at flight levels often blow at well over 50 miles an hour.

At this route's average burn of about 892 gallons per flight hour, those extra minutes cost about 202 gallons per flight, which is about 1.9 gallons or 18 kg of CO2 for each passenger on the slower direction. The route figure above averages both directions.

Time in the air by direction, 2025
DirectionAverage minutes in the airFlights
Washington, DC to Chicago97.715,191
Chicago to Washington, DC84.115,152

Fly or drive

Driving is about 713 miles by road, which we estimate as 1.17 times the straight-line distance. An average car emits about 212 kg of CO2 on the trip, at the EPA figure of 0.297 kg per vehicle-mile. Alone, that's 75% more than the 121 kg for a passenger on the flight.

With 2 people in the car, driving comes out lower per person than the flight (106 kg each, and 53 kg each for four). A larger SUV or pickup (0.394 kg per mile) would emit about 281 kg per vehicle.

CO2 per person by way of travel, Chicago to Washington, DCBar chart of kilograms of CO2 per person flying, driving or taking the train between Chicago and Washington, DC.050100150200Flight, average121 kgCar, driver alone212 kgCar, 2 people106 kgCar, 4 people53 kg
CO2 per person by way of travel, Chicago to Washington, DCBar chart of kilograms of CO2 per person flying, driving or taking the train between Chicago and Washington, DC.0100200Flight, average121 kgCar, driver alone212 kgCar, 2 people106 kgCar, 4 people53 kg
CO2 per person, Chicago to Washington, DC. Driving figures divide one car's emissions between the people in it. See flying vs driving for other trip lengths.

Flights are listed under the airline that operates them, so regional flying appears under the regional. How the CO2 and drive figures are worked out is in the methodology.

Routes with shared cities or nearby CO2 per mile

New York to Chicago125 kg CO2 per passenger over 730 milesWashington, DC to Boston100 kg CO2 per passenger over 383 milesAtlanta to Washington, DC104 kg CO2 per passenger over 554 milesLos Angeles to Chicago225 kg CO2 per passenger over 1,739 milesNew York to Nashville150 kg CO2 per passenger over 761 milesLos Angeles to Phoenix74 kg CO2 per passenger over 354 milesNew York to Detroit106 kg CO2 per passenger over 499 miles

Airports on this route: Ronald Reagan Washington National Airport, O'Hare International Airport, Washington Dulles International Airport, Baltimore/Washington International Thurgood Marshall Airport, Midway International Airport.

Airport and airline references

Source: US Bureau of Transportation Statistics (BTS), T-100 traffic and Schedule T-2 fuel filings; US EPA transport emission factors. See the methodology.

See all routes, or how the airlines compare overall on the airline pages.